1. Field of the Invention
The present invention relates to a process for preparing synthetic periplanone-B, the sex attractant and sex excitant pheromone of the American cockroach, Periplaneta americana.
2. Description of the Prior Art
Females of the species Periplaneta americana, the American cockroach, have long been known to produce an extraordinarily potent sex pheromone. Unfortunately, isolation and structural characterization of this pheromone were hampered due to the fact that the phermone is stored only in minute quantities (&lt;&lt;1 .mu.g) by individual cockroaches. Eventually, however, through a massive cockroach rearing and extraction program utilizing more than 75,000 virgin female cockroaches, C. J. Persoons, et al. were able to isolate two compounds, periplanone-A and periplanone-B. The major component was periplanone-B, which was found to be extremely active as a sex pheromone.
Subsequent structural studies of periplanone-B revealed that periplanone-B has the structure: ##STR1## However, the complete stereochemistry of the compound was not known until the work of W. C. Still et al. which revealed the compound to have the following structure: ##STR2## This structure may also be drawn as follows: ##STR3##
Since periplanone-B is such a strong sex attractant for the American cockroach, it would be highly desirable to incorporate it in, for example, compositions containing an insecticide effective against cockroaches. The male American cockroach would thus be attracted to the insecticide and killed by it. However, as noted above, it is virtually impossible to isolate natural periplanone-B from female cockroachhes in the quantities which would be required for use in commercial insecticides. Thus, a method for synthesizing periplanone-B was sought.
During their studies into the stereochemistry of periplanone-B Still et al. were successful in synthesizing periplanone-B via a process requiring about twenty-four steps. Since it is always desirable to simplify a synthesis or make it more efficient, improvements on the Still et al. technique were sought. The desired improved synthesis would provide a method for preparing periplanone-B relatively easily in quantities sufficient to make the compound available commercially.
A new synthesis for periplanone-B has now been discovered which requires only about one half the number of steps as the Still et al. process, and which makes it possible to prepare periplanone-B synthetically in commercial quantities.